Signaling apparatus



UNITED STATES PATENT FFICE.

ISAIAH H. FARNHAM, OF VVELLESLE Y, ASSIGNOR TO THE NEW ENGLAND TELEPHONEAND TELEGRAPH COMPANY, OF BOSTON, MASSACHUSETTS.

SIGNALING APPARATUS.

SPECIFICATION forming part of Letters Patent No. 444,108, dated January6, 1891. Application filed August 20, 1890. Serial No. 362,4=70. (Nomodel.)

To all whom it may concern: ber of stations. If, however, it be desiredto Be it known that I, ISAIAH H. FARNHAM, reapply the same principles inconnection with siding atVVellesley, in the county of Norfolk asingle-wire or earth-completed circuit, the and State of Massachusetts,have invented several closed and discontinuous bridges, or

certain Improvements in Signaling Apparaderived or branchcircuits,including,respecttus, of which the following is aspecification. 'ively, the call-bell magnets, the generating- Thisinvention concerns telephone-circuits, armature, and the telephone ortelephones, and is an improvement in that class of such will necessarilybe connected at each station circuits wherein a numberof stations areconin parallelism with the single line-wire, and

:0 nected with the same main line. It is espewill extend-therefrom toearth. In the above cially applicable to metallic'circuits. but canarrangement it is intended when the callalso be applied to single-wireor earth-comsending generator at any station is operated pleted linesinvolving the same principles. that the bells at all of the otherstations of The most approved modern practice of t-elthe circuit,including the bell at its own sta- 15 ephone-circuit construction andarrangement tion, shall ring, the current developed by where a number ofstations are to be consaid generator being divided among the elecnectedwith the same circuit is to construct tro-magnets of the said bells. Adistinctive a metallic circuit between the two terminal signal isassigned for each stat1on,and though stations,causingbothwires thereoftoloop-also all stations h ar every ring that one onl5 20 into all of theintermediate stations. The whose signal is given will respond. All ofelectric call-bell at each station is placed in the bell electro-magnetsused in connection a closed bridge or branch extending from one withsystems of the character indicated are of the main wires of the metalliccircuit to of high resistance and self-induction, they the other. Thecall-sending generator canbeing often wound up. to a resistance of five25 not be efficiently included serially in circuit hundred and sometimesto one thousand with the said bell, because if it were the reohms.sistance of the said bell would form virtually It is evident from whathas been stated that a portion of the internal resistance of the geninthe above class of circuits when any staerator, and make the latter sohigh that the tion-operator actuates his generator to call 0 systemwould not be self-regulating. Thereanother station the said generatorwill, dur- 8o fore the call-generator is included in a secing the saidcall, be connected in multiple 0nd but norinally-discontinuousbridge-cirare or in parallel with the ringing part or cuit between thetwo wires of the main cir call-bell magnets of said instrument. I havecuit, which bridge is closed only by and in ascertained that with thisarrangement the 35 the act of sendinga call-signal, and this'closclosedbridge of the call-bell magnet of the ure may be effected eithermanually, as a disstation sending the call becomes a very continctaction, or automatically, in a manner 'siderable obstacle to the strongand clear well understood and extensively employed ringing of the othercall-bells connected with in the operation of such generators. Thetelthe same line at distant stations-that is, it

4o'ephone at'eacli station also is included in a being by far thenearest call-bell bridge to normally-discontinuous bridge between thethe particular generator at this time in Opera main wires, which is heldopen by the prestion,will divert from themain linealargerpro once of thereceiving-telephone on its supportion of current than will any otheronesta port, but which is closed when the said retion or bell. Whilethis disadvantage is not 5 ceiver is removed for u e, so that thegenserious on a short line, it becomes of considerator andtelephone-bridge circuits are both erable moment in long ones, and islikely to shunted by the bell-bridge. This arrangebe very detrimental totheir satisfactory opi'n'ent has, for reasons unnecessary here toeration. It might be supposed that the easistate, been found extremelysatisfactory in est way to overcome or avoid this'disadvan- 50 theoperation of circuits connecting a numtage would be to so arrange theringingap- 10o pliances as to disconnect the call-bell at theringingestation altogether from the circuit during the operation ofsendinga call. It is, however, not practicable to do this, for thereason that the subscriber must hear his own bell ring or he would notknow or would not be satisfied that his generator was doingany work atall.

In View of the forcgoingconsiderations the object of my presentinvention is to prevent; a disproportionate amount of thecalling-current from being short-circuited at the calling- 5 station,and to arrange the appliances and circuits at each station in such a waythat outgoing signals shall be enabled to manifest themselves at thestation where they are prot duced without depreciating their effect uponthe call-bells at other stations. In carrying out these objects Iprovide means for increasing the resistance of the closed bell-bridgc orbranch circuit at the home or ringing station at the moment ofsendingthe call from thence.

I also do this by the same act which is ncces sary in order to send thecall, and thus impose no additional work, operation, or thought upon thestation-operator.

A practical means of embodying this invention is to place a suitableresistance (which may conveniently be formed of a coil or coils ofinsulated wire) in such relation to the pressbutton or automaticcircuit-closer orchanger which brings the generator into action that bythe act of operating the said button, key, or circuit-changer (whetheractuated manually or automatically) the said resistance shall beautomatically or without preconcerted action interposed in the circuitof the homebell magnets, whereby the said bell-bridge when a call 15being sent by the generator at the same station shall have itsresistance so raised or conversely have its conductivity so impairedthat, though much nearer to the said generator than are the bell-bridgesat the other stations, it shall present no greater facility for thepassage of the current than is presented by the bell-bridges at theother stations, respectively. In other words, the said bell-bridge,though physically in close proximity to the generator at its ownstation, is electrically and for all practical purposes in the samerelation with it and with the main circuit as if it were remotetherefrom. The interposed resistance may,it is evident, be regulated oradjustable but I prefer a fixed resistance on the ground of simplicity.I find it useful, however, in some cases to provide not simply aresistance-coil, but an electromagnetic coil, and in that event itbecomes an inductive resistance and involves the utilization ofself-induction. I am thus enabled to use a much smaller amount of wirecoils or number of convolutions than otherwise would be necessary, andconsequently a less-measured resistance.

In the drawings which accompany this specification, Figure 1 is adiagram showing aportion of a multiplestation telephone'circult, inwhich my invention is disclosed. Fig. 2 is an enlarged diagram of asmaller part of said circuit, showing two stations only, with theelectrical appliances and circuitconneetions fully drawn out at one ofthe said stations. Fig. 3 shows the embodiment of the invention in aconcrete apparatus, the several station applianccsbeingelectricallycombined in accordance with said invention; and Fig. -l shows a modifieddetail of the call-transmitting appliances, illustrating automatic meansfor bringing the generator into action.

The principle of my invention is fully disclosed in the diagram Fig. 1.A metallic circuit C is there indicated as extending bctween a number ofstations, these being designated, respectively, by the numerals l to 6.One of these may, if desired, beacentral station, as 1, or all may besubscribers stations, as would be the case if C were a private line. Theelectrical apparatus and its connections are alike at all subscribersstations. At each is a call-receiving electro-magnctic bell B, havingits electro-'1nagnets connected in a bridge orcross-wirecond uetor,forming a permanent connection between the two main-line wires L and Lof the main circuit (3. This bridge-connection is permanently closed atall stations, and the bells being respectively included therein are allconnected with the main circuit, and all will respond to signals sentfrom any station. At each station there is likewise a call-sendingmagneto-generator (i, also included in a bridge-conductor between thetwo main wires, whichbridge,however, is normally discontinuous, and onlyclosed while a call isactually being sent. A key or circuit-closer 7a isalso provided, and it will be seen that by means of its back or restingcontact the said key is in connection with the closed bell-bridge, butthat when pressed itisd isassociated therewith and caused to form a newconnection with the gcneratorbridge,which thereupon is closed, and byturning the handle the said generator can be actuated to send anoutgoing-call signal. Supposing that these appliances only wereprovided, as has heretofore been the case, if the line be long and ifthat one of the stations signaling be far from the others, it is obviousthat much of the current generated would be shunted through the bell atthe signaling-station, and thatthe other station-bells, deprived oftheirproper share of current, would be liable to ring imperfectly. Letit furthermore be supposed that station under these conditlons issending a signal. It is clear that bell B at said station, being muchnearer to its own generator than are any of the bells at other stations,will rob the said others of their due proportion of current, and thatthe major part of said current developed, leaving the generator G, say,by wire 12, will reach the other pole thereof by way of point g, section1t of main wire L, point 11, bell B, point 8, and key 7c. The home-bellonly will ring loudly, the others faintly. To remedy this fault Iprovide a suitable resistance R and connect it in the bell-bridgeserially with the bell B between the point 11 on line-wireL and 10 online-wire L but it is desirable that this resistance shall only bebrought into action at the station from which call-signals are beingsent, and that at all other stations it shall be temporarilyfunctionless. Therefore from a point 7 on the bell-bridge wire betweenthe bell-magnet B and the resistance R, I run a wire 6 to the back stopor contact a of the key It, the stem of the said key being connected at8 with the line-wire L Thus the normal bell-bridge extends from point 11on line-wire L to point 8 on line-wire L through the key and its backcontact, the resistance R being short-circuited or shunted out. Thiscondition is maintained at all stations where signals are beingreceived, so that the ringing-current coming into the several stationsis not weakened by the presence of the extra resistance in circuit, butcan exert its full force on the bell to give a good ringing efiect; butin sending a signal the crank or handle c of the magneto-generator isrevolved and at the same time the key is pressed. This, as alreadyexplained, closes the generator-bridge from the point you linewire L tothe point 8 on line-wire L the key 7.: having now become a part of thelatter bridge. It is to be observed, however, that the movement of thekey has not broken the circuit of the bell-bridge, which is still closedor continuous, but that it has removed the short circuit or shunt fromthe resistance R, which during the signal-sending operation is thusintroduced into the bell-circuit, raising the resistance thereof andpreventing the currents generated in G from being short-circuitedtherethrough.

In practice of course there are but two main-line station-terminals orpoints of attachment for the apparatus. This is made clear by Fig. 2,which also shows the telephone connections. The normal circuit throughthe station 3 is, as in all cases, by way of the permanently-closedbell-bridge, from point 11 on line L, by wire 15, bell B, point '7, wire2, back contact a, key it, point 10, wire 16, automatic switch 3, lowercontactspring 1; thereof, and wire 18, to point 8 on line-wire L Thisrepresents the station apparatus at rest, the bell included in the onlyclosed conductor through the station, the generator and telephonebridges open, and the resistance short-circuited or shunted. The key 70being depressed, the bell-circuit by way of e is broken; but the point10 is'reaehed through the resistance R. The generator bridge is alsoclosed, and follows the following route: from point 11, by way of wire12, magn eto-generator G, wire 22, key-anvil f, key 70, wire 23, topoint 10, and thence on the same path as the bell-bridge to point 8 online-wire L Only during the operation of the generator, therefore, isthe resistance R introduced to the'bell-bridge circuit.

the telephones while thelatter are being used.

At station 2, Fig. 2, the bell-magnets B and resistance R are indicatedin dotted lines.

Fig. 3 shows that the several station appliances hereinbefore describedare all, as usual, inclosed in a single box, which is indicated bybroken lines. The several instrumentalities and their electricalconnections are substantially identical with those described, as shownin Fig. 2, and are similarly distinguished by letters and figures ofreference, and it would therefore be useless to describe them again. Thefigure, however, is useful as indicating a suitable mechanicalarrangement. The two upper binding-screw terminals represent,respectively, the line connections 11 and 8, and of the six shown below,g and h are for the attachment of the receivingtelephone, '5 and j arefor the purpose of leading the local battery and primary coil-wires intothe bell-box, so that the primary circuit will be operated when theswitch 3. is depressed, and on and 'n are for connection of thetransmitter main-line helix.

Fig. 4 shows a simple mode of applying this invention to a bell whosegenerator-circuit is to be automaticallyclosed. Many magnetobellapparatuses are at the present time made which dispense with themanually-operated key It and have in lieu thereof a circuit-changer,which the movement. of the bell-crank actuates as a secondary function.

The essential features of the apparatus as described herein areunchanged, as are also the principal electrical connections. The key is,however, superseded by a flat contactspring 16*, which, as shown, ispermanently connected with the telephone-hook s, and which is capableunder certain conditions of making contact at its free end with the endzof the generator-armature axis, (representing one end of thegenerating-coils,) but which is normally held away therefrom and incontact with the point a, and thereby shunts the resistance R. Theaction of turningthe crank c by means of the notch device V, and in amanner well understood, gives the crankshaft q alateral motion againstthe coil-sprin g r, and its receding from the spring k permits thelatter to break contact with its back point a, and to close thegenerator-circuitat z, the resistance R being by the first part of theoperation introduced into the bell-circuit.

The resistance R, as stated, may be formed in Variousv ways. Ordinarily,diiferentiallywound helices of wire are the most conven ient.Frequently, however, as already explained, the electromagnetic coils maywith advantage be employed, and I regard their employment as beingdistinctively a feature of my invention.

The resistance required for the attainment of the best results may ofcourse vary with the length of the circuit, the resistance of thebell-magnets, and the distance between any special station and theothers; but a very good average resistance, if it be simply made ofcoiled wire, is the same as that of the associated bellmagnet. If aninductive resistance be employed, a much lower resistance will berequired.

Although I have throughout this specification referred tothe-call-receiving device as a call-bell, it is evident that any othersimilar device-such, for example, as a sounder or buzzer-is to beconsidered as involving the spirit of my invention.

I claim as my invention 1. In an electrical signaling systen1,anelectric circuit, an elcctro-magnetic signal-bell or equivalentelectro-magnetic signaling device in a permanently-closed branch of thesaid circuit, a signal-sending magneto-generator in a normally-openbranch of the said circuit, and means for increasing the resistance ofthe said bell-branch circuit while the said gene M01 is being operatedto send outgoing signals.

2. The combination, substantially as hereinbefo re described, with anelectric circuit extending between two or more stations, anelectro-magnetic call-receivin g device located at each station in apermanen tly-closed bridge or branch of said circuit, and a call sendinggenerator at each station in a normally-open bridge or branch of thesaid circuit parallel to the said closed branch, of means for closingthe said generator-circuit to send an outgoing signal and forsimultaneously increasing the resistance of the parallel bell branch atthe same station.

The combination of a metallic main-line circuit extending between andconnecting two or more stations, an electro-magn etic callbcll at eachstation in a permanently-continuous bridge between the two wires of saidcircuit, a call-sending generator at each station in a normally-openbridge, said bridge being when closed parallel with the bellbridge, aresistance, as described, in a shunt of the said bell-bridge, and means,as indicated, for breaking the said shunt and for introducing the saidresistance into the bellbridge circuit when the generator is beingoperated, and for withdrawing the same therefrom and for reinstating thesaid shunt when the generator becomes quiescent.

i. The combination of a metallic main-line circuit extending between andconnecting a number of stations, an electro-magnetic callbell at eachstation in a permanent bridge between the two wires of said circuit, areae moe sistancc adapted to be included with said call-bell in saidbridge, but normally shunted therefrom, a call-sending generator at eachstation in a parallel bridge of said circuit normally open, but adaptedto be closed in the act of sending signals, and a circuitchanging devicecontrolling the generatorbridge and the resistance-shunt and adapted toclose the one and open the other, and vice versa, according to itsposition.

5. In an electric signaling system, an elec tric main circuit extendingbetween two or more stations, a normally and permanently closed bridgeor derived circuit at each station connected with said main circuit andincluding an elect ro-magnetic call-receiving device, a normally-openbridge or derived circuit at each station, also connected with said maincircuit in multiple arc with the said bell branch and including asignal-sending generator, an inductive resistance, substantially asdescribed, connected with the said permanently-closed bell branch, butnormally shunted therefrom, and a circuit-changer controlling the saidresistance-shunt and normally maintaining the continuity thereof, butcapable of assuming a second position, in which the generator branch isclosed and the said resistance included in the bell-circuit, for thepurposes specified.

(3. A station apparatus for a multiple-station metallic circuitcombining two mainline terminals, one for each wire of the said metalliccircuit, a permanently-continuous conductor uniting the said terminalsand forming a bridge between them, an electro magnetic call-bell, and aresistance included in said bridge, combined with an0rinally-discontinuous independent bridge also extending between saidterminals parallel to the first, a call-sending magneto-generator in thecircuit of the said normally-open bridge, a shunt-circuit normallyclosed round the bellbridge resistance, and a circuit-changing key orswitch normally forming, together with its back contact, a portion ofsaid shunt-circuit and maintaining the continuity thereof, but adaptedwhen operated to form, together with its front contact, a portion of thegeneratorbridge and to complete the same,whcreby the act; of sending thesignal is caused to add resistance to the bell-bridge.

7. The combination, substantially as described herein, of an electriccall-bell and a call-sending magneto-generator connected, respectively,in a permanently-closed and a normally-open bridge between theline-terminals of a telephone-station apparatus, with a suitableresistance and a circuit-changer controlling the same and adapted toconnect the said resistance in the call-bell circuit during theoperation of the said generator in sending outgoing signals, but towithdraw the same therefrom when said operation is intermitted,substantially as and for the purposes set forth.

8. The combination, in a tclephone'signaling system, of a metallic maincircuit, a number of telephone-stations interconnected thereby, apermanently-eontinuousbridge or cross-conductor at each station,including the call-bell magnets, a resistance-coil at each station, alsoincluded in the said bell-bridge, but normally shunted orshort-circuited, a normally-discontinuous independent bridge orcross-conductor at each station, a call-sending magneto-generatorconnected with the same and arranged to be included therein when thesaid cross-wire is closed, and a circuit-changer constructed to closethe said open cross-Wire during the operation of said generator and tosimultaneously and automatically break the resistance-shunt,whereby thesaid extra resistance may remain shunted at all stations except thatsending a call and shall at said call-sending station be introduced intothe bell branch, substantially as described.

In testimony whereof I have signed my name to this specification, in thepresence of two subscribing witnesses, this 6th day of August, A. D.1890.

ISAIAH I-l. FARNHAM. Witnesses:

GEO. WILLIS PIERCE, FRANK C. LOOKWOOD.

